Atopic dermatitis (AD), widely known as eczema is a chronic inflammatory skin disease that affects 2 to 17% across adult populations worldwide.
The risk factors for adult AD are complex. Some studies have reported a Mediterranean diet and fermented milk products may offer protective factors for eczema, while others have suggested that a high intake of refined grains, red meat, cured food commonly referred to as a Western diet, may increase risk of AD and inflammation.
However, the effect of processed foods in Chinese diets on AD remains unclear, “the huge differences between Chinese and Western diets make the conclusions of previous studies impossible to be well generalised,” researchers wrote in Frontiers in Nutrition.
In China, processed foods include smoked/cured/roast meat or beef, sausage, luncheon meat, as well as pickles as well pickled mustard tubers, salted vegetables, and sauce vegetables. Salt is ubiquitously used in the procedure of processing and preserving.
In this study, the consumption of pickles and processed meats one to three times per week was associated to a 35% and 44% additional risk of AD respectively.
Study design
A total of 15,062 participants comprising 3,781 rural residents, 5,111 civil servants, and 6,170 workers were recruited in this study.
Researchers used data from three cross-sectional studies. Rural residents were participants of the Hunan Rural Resident Chronic Disease Study, civil servants from the Hunan Government Employee Health Study, and automobile manufacture workers from the Dongfeng-Tongji Cohort Study.
The intakes of processed meats and pickles were collected through the food frequency questionnaire (FFQ), which was the same used across the three studies.
A spot urine test was used to calculate the intake of sodium.
AD was diagnosed by certificated dermatologists during the field health examination.
Across all three studies, the prevalence of AD was highest among civil servants (6.46%), followed by workers (3.14%) and rural residents (1.59%).
The mean intake of sodium around 8.38 g/d in AD patients and 8.24 g/d in healthy controls. There was no statistical significance.
Processed meat and pickles
Findings revealed processed food as a risk factor for AD in 15,062 Chinese adults based on a pooled analysis of three cross-sectional studies.
Those who consumed pickles one to three times per week had a significantly greater risk of AD, a 33% risk, compared to those who hardly ate pickles.
Those who ate processed meats one to three times per week had a significantly 44% risk of getting AD, compared to non-consumers.
Researchers speculate that the sodium in processed foods may have an association with the risk of AD by affecting immune-related pathways.
The pathogenesis of AD is attributed to immune-related abnormalities and skin barrier impairments.
In this study, researchers think excessive sodium intake can affect the epidermal barrier microenvironment.
In addition, some observational studies report that AD patients have changes in their intestinal flora and metabolites compared to healthy people. These include a decreased abundance of Bifidobacterium, Akkermania muciniphila, and Rumenococcus gnavus, and decreased faecal short-chain fatty acids (SCFAs) and other metabolites.
“The intake of red and processed meat is also related to the decline of bifidobacteria and short-chain fatty acids (SCFAs). SCFA can promote mucus secretion, protect and maintain the intestinal mucosal barrier and the intestinal microenvironment, and the decline of SCFA such as butyrate is closely related to the risk of many diseases,” researchers said.
Hence, they think processed foods intake is associated with AD in Chinese adults, which might be related to sodium intake. However, they also highlighted that more accurate and precise methods of dietary exposure assessment were needed for further validation.
For this study, one limitation was the estimation of sodium intake based on spot urine, which tend to overestimate.
Source: Frontiers in Nutrition
https://doi.org/10.3389/fnut.2021.754663
“Processed Food and Atopic Dermatitis: A Pooled Analysis of Three Cross-Sectional Studies in Chinese Adults”
Authors: Yajia Li, et al.